Problem: In her math class, Jessica took 4 quizzes. Her scores were 75, 78, 84, and 87. What was her average score on the quizzes?
Solution: The average is the sum of her scores divided by the number of scores. There are 4 scores and their sum is $75 + 78 + 84 + 87 = 324$ Her average score is $324 \div 4 = 81$.